Add sha1sum program as a test/application of the SHA-1 computation.

sha1sum.c

@@ -0,0 +1,39 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+#include "sha1.h"
+
+unsigned char buf[0x8000];
+
+int main(int argc, char **argv) {
+    struct sha1_context ctx;
+    FILE *file;
+    size_t count;
+    int i;
+
+    srand(time(NULL));
+
+    if (argc != 2)
+        return EXIT_FAILURE;
+
+    file = fopen(argv[1], "rb");
+    if (file == NULL)
+        return EXIT_FAILURE;
+    
+    sha1_init(&ctx);
+    do {
+        count = (rand() & 0x7FFF) + 1;
+        count = fread(buf, 1, count, file);
+        sha1_update(&ctx, buf, count);
+    } while (count != 0);
+    
+    fclose(file);
+    sha1_finalize(&ctx);
+    
+    for (i = 0; i < 20; i++) {
+        printf("%02x", ctx.hash[i]);
+    }
+    printf("\n");
+    
+    return 0;
+}